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    SubjectRe: [PATCH] 2.6 SGI Altix I/O code reorganization
    Jesse Barnes wrote:

    Hi Jesse/Grant,

    May be my response to Grant got lost .. anyway, here it is again.

    > On Wednesday, October 6, 2004 12:54 pm, Grant Grundler wrote:
    > > Colin,
    > > thanks for ACKing the feedback.
    > > I think there is still some confusion...
    > >
    > > On Wed, Oct 06, 2004 at 02:09:54PM -0500, Colin Ngam wrote:
    > > ...
    > >
    > > > > Mathew explained replacing the raw_pci_ops pointer is the Right Thing
    > > > > and I suspect it's easier to properly implement.
    > > >
    > > > I believe we did just that. We did not touch pci_root_ops.
    > >
    > > Correct. The patch ignores/overides pci_root_ops with sn_pci_root_ops
    > > (which is what I originally suggested).
    > >
    > > Mathew's point was only raw_pci_ops needs to point at a different
    > > set of struct pci_raw_ops (see include/linux/pci.h).
    >
    > Though now what's there seems awfully redundant, wouldn't you say? Just
    > allowing direct access to pci_root_ops is a much simpler approach and gets
    > rid of a bunch of extra, unneeded code (i.e. closer to Pat's original
    > version).

    The original mod, we took out the static from pci_root_ops() so that we can use
    it in io_init.c. We thought that would be the cleanest.

    We do not want to change pci_raw_ops(). It is doing exactly what we need, now
    that sn platform has the support for SAL pci reads and writes support.

    >
    >
    > > > Yes, would anybody allow us to make a platform specific callout
    > > > from within generic pcibios_fixup_bus()???
    > >
    > > If it can be avoided, preferably not. But that's up to Jesse/Tony I think.
    >
    > If it was made a machine vector that's a no-op on everything but sn2, I think
    > it would be fine. Doing it for the general sn_pci_init routine would let us
    > get rid of the check for ia64_platform_is("sn2") in one of the routines, I
    > think (which is nice if only for the consistency).
    >
    > > Can you quote the bit of the patch which implements "if the bus does not
    > > exist" check?
    > > I can't find it.
    >
    > In the current code it's:
    >
    > for (i = 0; i < PCI_BUSES_TO_SCAN; i++)
    > if (pci_bus_to_vertex(i))
    > pci_scan_bus(i, &sn_pci_ops, controller);
    >
    > which causes the next loop to only fixup existing busses. But I don't see it
    > in the new code.

    Probably not clear to all:

    +/*
    + * sn_pci_fixup_bus() - This routine sets up a bus's resources
    + * consistent with the Linux PCI abstraction layer.
    + */
    +static void sn_pci_fixup_bus(int segment, int busnum)
    +{
    + int status = 0;
    + int nasid, cnode;
    + struct pci_bus *bus;
    + struct pci_controller *controller;
    + struct pcibus_bussoft *prom_bussoft_ptr;
    + struct hubdev_info *hubdev_info;
    + void *provider_soft;
    +
    + status =
    + sal_get_pcibus_info((u64) segment, (u64) busnum,
    + (u64) ia64_tpa(&prom_bussoft_ptr));
    + if (status > 0) {
    + return; /* bus # does not exist */
    + }
    +
    + prom_bussoft_ptr = __va(prom_bussoft_ptr);
    + controller = sn_alloc_pci_sysdata();
    + if (!controller) {
    + BUG();
    + }
    +
    + bus = pci_scan_bus(busnum, &sn_pci_root_ops, controller);
    + if (bus == NULL) {
    + return; /* error, or bus already scanned */
    + }

    The sal_get_pcibus_info() will fail if we do not find that bus number. If it
    fails, we do not call pci_scan_bus()


    Thanks.

    colin

    >
    >
    > > > One favour. Would you agree to letting this patch be included by Tony
    > > > and we will come up with another patch to fix the 2 obvious items listed
    > > > above? It will be great to avoid spinning this big patch.
    >
    > The patch is ok with me, I think it's a big improvement over what's there in
    > terms of readability.
    >
    > I just checked out sn_set_affinity_irq() and it's a bit hard to see what's
    > going on. Why does a new interrupt have to be allocated? Also, it looks
    > like the kfree() is one line too high, if sn_intr_alloc fails, we'll leak
    > new_sn_irq_info.
    >
    > Jesse

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